Devices for imaging body cavities or passages in vivo are known in the art and include endoscopes and autonomous encapsulated cameras. Endoscopes are flexible or rigid tubes that pass into the body through an orifice or surgical opening, typically into the esophagus via the mouth or into the colon via the rectum. An image is formed at the distal end using a lens and transmitted to the proximal end, outside the body, either by a lens-relay system or by a coherent fiber-optic bundle. A conceptually similar instrument might record an image electronically at the distal end, for example using a CCD or CMOS array, and transfer the image data as an electrical signal to the proximal end through a cable. Endoscopes allow a physician control over the field of view and are well-accepted diagnostic tools. However, they do have a number of limitations, present risks to the patient, are invasive and uncomfortable for the patient, and their cost restricts their application as routine health-screening tools.
Because of the difficulty traversing a convoluted passage, endoscopes cannot reach the majority of the small intestine and special techniques and precautions, that add cost, are required to reach the entirety of the colon. Endoscopic risks include the possible perforation of the bodily organs traversed and complications arising from anesthesia. Moreover, a trade-off must be made between patient pain during the procedure and the health risks and post-procedural down time associated with anesthesia. Endoscopies are necessarily inpatient services that involve a significant amount of time from clinicians and thus are costly.
An alternative in vivo image sensor that addresses many of these problems is capsule endoscope. A camera is housed in a swallowable capsule, along with a radio transmitter for transmitting data, primarily comprising images recorded by the digital camera, to a base-station receiver or transceiver and data recorder outside the body. The capsule may also include a radio receiver for receiving instructions or other data from a base-station transmitter. Instead of radio-frequency transmission, lower-frequency electromagnetic signals may be used. Power may be supplied inductively from an external inductor to an internal inductor within the capsule or from a battery within the capsule. The wireless-based capsule camera system will require a patient to wear a wireless transceiver and data recorder to receive and record the captured images. The capsule camera may stay in the body for over ten hours. Therefore, the patient may have to wear the wireless data receiver pack for extended hours which may be uncomfortable.
An autonomous capsule camera system with on-board data storage was disclosed in the U.S. patent application Ser. No. 11/533,304, entitled “In Vivo Autonomous Camera with On-Board Data Storage or Digital Wireless Transmission in Regulatory Approved Band,” filed on Sep. 19, 2006. The capsule camera with on-board storage archives the captured images in on-board non-volatile memory. The capsule camera is retrieved upon its exiting from the human body. The images stored in the non-volatile memory of the retrieved capsule camera is then accessed through an output port on in the capsule camera. The images can be processed and displayed on viewing station and examined by diagnostician. In order to reduce the required storage space, the images captured usually are compressed using image/video compression. On the other hand, the capsule camera has to provide sufficient storage capacity for the captured. The on-board storage has to be able to retain the captured image data for a period of time without any power supplied. Therefore, non-volatile memory has to be used for on-board storage. The total number of stored images may be quite large and there is a trend of demanding for higher resolution in order to provide more accurate diagnosis based on images with more details. Therefore, multiple non-volatile memory chips may be required to fulfill the storage capacity requirement. Besides the multiple non-volatile memory chips required, the system may also include multiple processing chips to perform various tasks such as motion metric evaluation, image/video compression, and system control. Therefore, a capsule camera with on-board storage faces the challenge to pack multiple chips and various components such as sensor, LED light source, batteries into the capsule camera housing. It is very desirable to pack the multiple chips in a compact means to make the capsule camera as small as possible for easy to swallow.